Followup on some previous emails I sent this week around sticky sessions
and OIDC backchannel requests.
In shortcut, it would be ideal if we can achieve that backchannel
requests (code-to-token, refresh token, logouts etc) can participate in
same sticky session like the browser request. It may be possible in some
cases (our adapters, some loadbalancers, see previous email I sent this
week) but not everytime. And looks we would need to support the case
when it's not possible.
I can start with code-to-token request as it's slightly more complicated
then the others due to the reasons:
1) code must be single-use per OAuth2 / OIDC specification
2) userSession may not yet be available. In case that we use ASYNC
channel for communication between datacenters for transfer userSession
(which I think should be the default due to performance reasons), then
this example flow can happen:
- user successfully authenticated and userSession was created on DC1.
- code-to-token request is sent by the adapter to DC2. Note that this
request is usually sent very quickly after userSession is created.
- DC2 didn't yet received the message from DC1 about the new
userSession. So this userSession not yet available here.
Questions:
1) Could we remove a need from code-to-token endpoint to lookup
userSession? I see this as an option as long as code itself is JWT
signed with realm HMAC key encapsulating some info about user,
session_state etc. Among other things, this would require some
refactoring of protocolMappers (as userSession won't be available when
tokens are generated). But isn't it bad for security to have some claims
directly to the code? It is query parameter, which may end visible in
browser history. IMO this is not big issue, but not 100% sure..
2) Another option is let the code-to-token endpoint wait until
userSession is available. Then we would need support for asynchronous
requests? I can see blocking undertow workers in waiting (something
based on java.util.concurrent.Future) can be an issue and potential for
DoS? Still even with asynchronous, the request times can be quite long.
3) Can we encourage people to use sticky sessions at least for
code-to-token endpoint? We can add the route directly to the code
itself, so the URL will look like:
http://apphost/app?code=123.node1&state=456 . Many loadbalancers seem to
support sticky session based on URL part. But there is also
response_mode=form_post when the code won't be available in the URI.
4) Is it ok to have option to relax on code one-time use? Otherwise in
cross-DC and without sticky session, the every code exchange may require
SYNC request to another DCs to doublecheck code was not used already.
Not good for performance..
For now, I can see some combination of 1,3,4 as a way to go. WDYT?
Marek